I believe they were supposed to be critical of each other,not a bad idea,providing they had respect for each other.
the main problem with groups like this is that there will always be a pecking order,however hard Ewan would have tried to not let this happen he would have been number one in the heirarchy.
presumably, Ewans singing was criticised by other members.
the important thing to remember is that everyone was there voluntarily,therefore they thought that the criticism would improve them as singers.
there must have been a lot that singers could learn from Ewan othewr than purely singning,Stagecraft, presentation ,etc
Did the critics group ever discuss songwriting?,